Alloy



' in one alloy the optimum properties for a given f application. Forexample, it may be found that Patented June 23, 1936 I ALLOY Roy E.Paine, Oakland, Calif., assignor, by mesne assignments, to MagnesiumDevelopment Corporation, a corporation of Delaware No Drawing. Originalapplication October 4,

1933, Serial No. 692,135. Divided and this applicationNovember 15, 1935,Serial No. 49,970

2 Claims. The invention relates to magnesium-base alloys and is directedto the development of alloys of this class which have good corrosionresistance, particularly in the cast and in the cast and heat treatedcondition.

The art of casting magnesium presents many practical diiliculties whichmust be surmounted before the true commercial possibilities of magnesiumcastings can be fully realized. An alloy which is suitable for oneapplication may be entirely unsuited to another and, as a consequence,it is frequently necessary to sacrifice desirable characteristics of thealloy in order to more fully realize the advantages of some one or moreimportant characteristics. Thus a compromise must quite frequently bemade in order to approach corrosion resistance can be sacrificed to acertain extent to obtain higher tensile strength, yield point, hardness,or similar mechanical properties.

Again, tensile strength may be sacrificed in order istics.

to obtain proper casting or working character- It is an object of thepresent invention to develop magnesium alloys which will combine to .amaximum degree the characteristics of cor-' rosion resistance, favorablemechanical properties, workability, susceptibility to improvement byheat treatment and adaptability to sand cast-. mg.

A further object is the provision of magnesium alloys characterized bytheir susceptibility, to be improved in mechanical properties bysuitable thermal treatments. A further object is the provision ofmagnesium-base, alloys characterized by good corrosion resistance ineither the cast or in thecast and heat treated condition.- -A furtherobject is the provision of magnesium alloys possessing excellent castingcharacteristics. A further object is the provision of magnesium-, basealloys .susceptible, within certain ranges, to mechanical deformation;

I have discovered that magnesium-base alloys containing from 0.5 percent to 22 per cent of lead possess to an appreciable degree thecollective characteristics of I alloys whichare resistant to corrosion,alloys which may be readily cast, alloys which, are susceptible toalteration of properties by thermal treatments, alloys having favorablemechanical properties, and alloys which, within a restricted range, maybe worked by extrusion,

forging, or other means of mechanical deformation. I In accordance withmy invention lead may be present in amounts as low as 0.5 per cent. The

preferredcastingalloys arethose containing above about 5 per cent oflead since it is in these alloys that themost pronounced combination ofthese different properties is obtained. The alloy may be worked byextrusion over a range of from about 0.5 per cent to about 22.0 per centof lead. As an all around casting alloy I have found a magnesium alloycontaining 5 to per cent of lead to be particularly adapted to generalfoundry purposes. Alloys falling within this preferred range ofcomposition as well as other alloys comprised within the broader limitspreviously defined, have been subjected to severe tests designed toproduce accelerated corrosion. Sand cast test bars poured in accordancewith the best casting practice in theart were subjected to corrosiontests in the as cast and in the heat treated conditions; In the examplereferred to the heat treatment was carried out at about 459 centigradefor about 20 hours followed by quenching in water, and both heat treatedand unheat treated test bars were subjected to that corrosion test whichcomprises alternately immersing the metal in, and removing it from, a3per cent sodium chloride solution for about 80 hours,'

a treatment referred to hereinafter as the altern'ate immersiontreatment.

There are certain elements which may be added to the binarymagnesiumdead alloys to.

particular advantage. Such, for instance, are the metals calcium,cadmium and zinc, These may be added singly or in combination with eachother, the zinc in amounts between about 1.0

per cent and 10.0 per cent, the calcium between about 0.1 per cent and2.0 per cent; and the cadmium between about 1.0 per cent and 10.0

per cent. These alloying elements are substantial equivalents asindicated by their'susceptibility to thermal treatment in magnesium-leadalloys. The calcium favorably aflects the casting properties of thealloy without markedly decreasing its corrosion resistance. I nesiumalloy containing 2134 per cent of lead and 0.25 per cent of calciumshows, in the as cast condition, a strength loss of only 17 per centafter alternate immersion in a 3 per cent sodium chloride solution forabout 80 hours, while a heat treated magnesiumralloy containing about 5per cent of lead to which about 0.25 per cent of calcium-had been addeddid not undergo any appreciable loss in strength under the foregoingcorrosion conditions; the heattreatmentin this case was atreatment atabout 450? centigrade for about'20 hours. An alloy of magnesium withabout 5. 1- per cent of lead and 10.0 per cent of For instance, a.maglead, 1.0 per cent calcium, balance magnesium;

cadmium had in the sand cast condition a tensile strength of about24,650 pounds per square inch and an elongation of about 9.8 per cent in2 inches. After a heat treatment of about 20 hours at about 450centigrade its tensile strength ad increased to about 25,140 pounds persquare inch and its elongation to 10.3 per cent in 2 inches. After analternate immersion corrosion test for 80 hours the loss in strength wasonly 30 per cent. A similar result was obtained with a magnesium-basealloy containing about 5.3 per cent of lead and about 5.0 per cent ofcadmium. An alloy of magnesium with about 5.0 per cent of lead and 5.0per cent of zinc had in the sand cast condition a tensile strength ofabout 23,370 pounds per square inch. After a thermal treatment of about20 hours at 450 centigrade followed by an aging treatment of about 20hours at 150 centigrade its strength had increased to about 25,710pounds per square inch. After an alternate immersion corrosion test of80 hours the loss in strength was only 12 per cent. Another alloy ofmagnesium with about 5.2 per cent of lead and 3.2 per cent of zinc undersimilar conditions lost only about 10.per cent after 80 hours alternateimmersion in the corrosive solution. As a preferred composition foralloys of this nature I advise (l) 5.0 percent (2) 5.0 per cent lead,5.0 per cent cadmium, balance magnesium; (3) 5.0 per cent lead, 5.0 percent zinc, balance magnesium. If more than one of the elements calcium,cadmium, or zinc be present simultaneously; I prefer not to exceed atotal of 10.0 per cent for these' elements.

One of the disadvantages of the alloys described herein which may affecttheir use in certain applications, particularly where high strength is aleading or very material considerae tion, is the fact that the grainstructure of these alloys (with or without calcium) tends to be coarse.I have found that the metals aluminum and silicon form a class ofalloying elements which may be added to magnesium-lead alloys and aresubstantially equivalent in this respect that they materially refine thegrain structure of the alloy. Aluminum, for instance, can be added overa wide range, such as between 1.0 and 15.0 per cent; silicon may beeffectively present for this purpose in amounts of about 0.1 to 2.0

per cent. when used in combination it is advisable that the totalcontent of aluminum and silicon does not exceed 15.0 per cent. In thepreferred practice of my invention I have found that the best resultsare usually obtained when the aluminum is present in amounts between 5and 10 per cent.

Asa preferred magnesium-lead-silicon composition Iuse a magnesium-basealloy containing 7.0 per cent of lead and 0.5 percent of silicon. As apreferred magnesium-lead-aluminum alloy I use a magnesium-base .alloycontaining 7.0 per cent of lead and 5.0 per cent of aluminum. When thealuminum and silicon are used in conjunction I prefer to use a total ofabout 5.0 per cent of aluminum and silicon combined, for instance about4.0 per cent aluminum and 1.0 per cent silicon.

Manganese alone may be added to magnesiumlead alloys in amounts between0.1 per cent and 1.0 per cent and has a stabilizing effect upon thealloy properties in that it raises the hardness slightly, does notmaterially decrease the corrosion resistance, and adds to the matrix ofthe not only in an increase in tensile strength but also in surfacehardness. An alloy of this nature containing about 8.0 per cent of leadand 0.85 per cent of manganese lost only 6 per cent of its originalstrength after hours alternate immersion in a 3 per cent aqueoussolution of sodium chloride and in the solution heat treated conditionlost only 7 per cent of its strength in the alternate immersiontreatment. A magnesium alloy containing about 10.37 per cent of lead hadlost only about 10 per cent of its strength at the expiration of thisperiod as compared with certain other commercial alloys, such as, forinstance, the well known magnesium alloy containing about 7 per cent ofaluminum and 0.4 per cent of manganese which, at the end of 40 hours ofalternate immersion, had lost about 60 per cent of its strength.

Very favorable alloys can be compounded by using as a base an alloy ofmagnesium, lead and aluminum and making additions thereto of at leastone of the class of metals tin, manganese or zinc. The lead can be usedin amounts from about 0.5 per cent to about 22.0 per cent, the .aluminumfrom about 1.0 per cent to about 15.0

' per cent, the tin from about 1.0-per cent to about 15.0 per cent, themanganese from about 0.1 per cent to about 1.0 per cent, and the zincfrom about 1.0 per cent to about 10.0 per cent. A sand cast alloy withinthis range had, in the as cast condition, a tensile strength of 27,500pounds per square inch and an elongation of 5.7 per cent in 2 inches.After a thermal treatment of 16 hours at 315 centigradethe alloy had atensile strength of 29,640 pounds per square inch and an elongation of6.0 per cent in 2 inches. Some of the heat treated specimens were thengiven an alternate immersion treatment for 40 hours and after thetreatment the specimens had a tensile strength of 28,413 pounds persquare inch and an elongaaluminum and 0.4 per cent of manganese. Aspreferred compositions for alloys of this nature I advise (l) 7.0 percent of lead, 7.0 per cent of aluminum, 2.0 per cent tin, balancemagnesium; (2) 7.0 per cent lead, 7.0 per cent aluminum, 2.0 per centtin, 0.5 per cent manganese, balance magnesium; (3) 7.0 per cent lead,7.0 per cent aluminum, 2.0 per cent tin, 2.0 per cent zinc, balancemagnesium. I

Two alloy compositions within this range which I have used to advantageare as follows: A magnesium-base alloy containing 8.0 per cent of alu-3.0 per cent of lead, 0.4 percent of manganese, 1.0 per cent of zinc,and 3.0 per cent of tin; a'magnesium-base alloy containing 8.0 per centof aluminum, 1.0 per cent of lead, 0.4 per cent of manganese, 1.0 percent of zinc, and 1.0 per cent of tin.

The addition of lead to the magnesium-aluminum-manganese alloysincreases very considerably the corrosion resistance of these alloys,since with the addition of about 7 per cent of lead to an alloycontaining 7 per 'cent of aluminum and 1 per cent of manganese, the lossof strength after the alternate immersion test was only about 30 percent, as compared with about 60 per cent of the same alloy without lead.I

Alloys of magnesium with lead, aluminum, and manganese have beendisclosed hereinabove. I have discovered that if to a base alloy ofmagnesium-lean-aluminum-manganese I add one or more of the class ofmetals calcium or cadmium, the resulting alloys: become considerablymore susceptible to variation of properties by thermal treatments andtheir hardness can be markedly increased by artificial aging afterthermal solution treatments. In these alloys the lead content shouldrange'from about 0.5 per cent to about 22.0

per cent, the aluminum from about 1.0- percent to about 15.0 per cent,and the manganese from about 01 per cent to about 1.0 per cent. To theseelements as a common base I add the elements calcium, or cadmium, singlyor in combination, the calcium in amounts from about 0.1 per cent toabout 2.0 per cent, the cadmium from about 1.0 per cent to about 10.0per cent. As an example of an alloy of this nature, a sand cast specimenof a magnesium-base alloy containing about 10.0 per cent of lead, about7.0

per cent of aluminum, about 0.4 per cent of manganese and about 5.0 percent of cadmium, had

in the cast condition a tensile strength of about 23,200 pounds persquare inch. After a thermal solution treatment of 21'hours at about 430centigrade the tensile strength of the alloy had increased to about36,000 pounds per square inch, a gain in strength of about 55 per cent.The

same alloy after the solution treatment had a Brinell hardness of about61 and this hardness was raised to about 84 by an additional agingtreatment of hours at about 175 centigrade, the tensile strengthincreasing slightly to about 37,000 pounds per square inch.

Similarly a magnesium-base alloy containing about 5.0 per cent of lead,7.0 per cent of aluminum, 10.0 per cent of cadmium, and 0.4 per cent ofmanganese had in the sand cast condition a tensile strength of about24,000 pounds per square inch. After a. thermal treatment of 21 hours atabout 430 centigrade the alloy had a tensile strength of about 35,000pounds per square inch. An additional aging treatment raised the Brinellhardness of the alloy from about 61 to about 79.

Similarly, a magnesium-base alloy containing about 5.0 per cent of lead,10.0 per cent of cadmium, 7.0 per cent of aluminum, 1.0 per cent ofmanganese, and 0.25 per cent of calcium had in the sand cast condition atensile strength of about 24,290 pounds per square inch. After a thermaltreatment of 20 hours at about 430 centigrade this alloy had a tensilestrength of about 33,200 pounds per square inch. After an additionalthermal treatment of about 20 hours at about 150 centigrade the strengthincreased to about 35,600 pounds per square inch and the Brinellhardness from about 47 to about 66.

Another magnesium-base alloy containing about 10.0 per cent of lead, 7.0percent of aluminum, 5.0 per cent of cadmium, 0.4 per cent of manganese,and 0.1 per cent of calcium, had in the sand cast 1 condition a tensilestrength of the aluminum.

of this nature I advise 7.0 per cent lead, 7.0 per cent aluminum and 0.4per cent manganese. If

not exceed about 10.0 per cent for preferred pur- 5 poses.

The addition of zinc in amounts from about 1.0 per cent to about 10.0per cent to magnesiumlead alloys containing aluminum'and silicon incombination decreases the linear shrinkage, thus favorably affecting thecasting properties, and also increases the corrosion resistance andraises the yield point of these alloys. In alloys of-this type the leadshould range from 0.5 per cent to 22.0 per cent, the aluminum from 1.0per cent to 15.0 per cent, and the silicon from 0.1 per cent to 2.0 percent, but the total amount of aluminum and silicon should preferably notexceed 15.0 per cent.

A useful alloy of this nature is a magnesiumbase alloy containing about10.0 per cent lead, 8.0 per cent aluminum and 3.25 per cent zinc.Another useful composition is attained by substituting about 1.0 percent silicon for part or all of An alloy similarly improved in castingproperties, although not to such a decided extent, is one containingfrom about 0.5 per cent to 22.0 per cent of lead, from about 1.0 percent to about 10.0 per cent of zinc, and from about 0.1 per centto about2.0 per cent of silicon. A favorable alloy within this range is amagnesium-base a1loy,consisting of about 10.0 per cent of lead, about3.25 per cent of zinc, and about 1.0 per cent of silicon, the balancebeing substantially magnesium.

In making up alloys of the compositions disclosed hereinabove the alloysmay be compounded by any of the methods known in the art. In casting thealloys recourse may be had to the protective measures disclosed inexisting patents and the published literature relating to easilyoxidizable metals. The alloys, especially the magnesium-lead binaryalloys, may be extruded over the entire disclosed composition range, butother types of mechanical deformation such as rolling or forging shouldbe carried on with due regard for the fact that as the percentage oftotal added alloying elements increases, the necessity for precaution inworking the alloy also increases.

It is my object to retain, as far as possible, the advantages of the useof magnesium base, such as low specific gravity, while securing inaddition the hereinabove disclosed benefits accruing from the additionsof the other alloying elements herein outlined. Accordingly, where inthe appended claims the term magnesium-base alloy is used, it refers toan alloy containing more than approximately per cent of magnesium.

This application is a division of my copending.

application Serial No. 692,135, filed October 4,

ROY E. PAINE.

